a bun in the oven
when a woman is pregnant, and it’s like a baby is baking inside her, hot and messy
My sister is a bun in the oven. She’s been eating ice cream like it’s her job.
She said, 'I’m a bun in the oven, and I’m not going to let you forget it.'
That lady is a bun in the oven. I can hear the baby yelling from inside her.